Multi-chip module and heat-sink cap combination

Abstract

A multi-chip module and heat-sink cap assembly and method of fabrication, which provides sufficient cooling for higher power density chips. The heat-sink cap has heat-sink columns disposed over each chip on a substrate. The heat-sink columns are interconnected by flexible members to provide a unitary cover. Thin film metallization of at least a portion of the mating surfaces of the substrate, chips and heat-sink column permits soldering of the cap to the chips and substrate to form the package which is a mechanically stable structure with no degradation of interconnection fatigue life due to thermal cycling of the assembly when in use.

What is claimed:  
     
       1. A multi-chip module and heat-sink cap combination manufactured by the process of: 
       providing a substrate with a plurality of chips fixed to and arrayed in a specific pattern thereon;  
       forming a heat-sink cap from a material having a coefficient of thermal expansion similar to that of the substrate comprising a plurality of individual heat-sink columns, each individual heat-sink column having a peripheral surface adapted to be bonded to a peripheral surface portion of a mating individual chip, said heat-sink columns interconnected by flexible members, the heat-sink columns arrayed in an identical pattern to the chips on the substrate;  
       depositing a conductive thin film on that portion of the peripheral surfaces of the chips and the heat-sink columns that are to be bonded together;  
       assembling the substrate and the heat-sink cap with solder between mating portions of the heat-sink cap and the chips and between the heat-sink cap and the substrate; and  
       reflowing the solder to effect bonding of the heat-sink to the substrate and the chips.  
     
     
       2. A multi-chip heat-sink cap combination according to  claim 1  wherein the heat-sink cap with the flexible connections between the heat-sink columns is formed as a unitary structure. 
     
     
       3. A multi-chip heat-sink cap combination according to  claim 1  wherein the heat-sink cap is formed from a material selected from the group consisting of aluminum nitride, aluminum-silicon carbide alloy, silicon carbide, copper-tungsten, aluminum and copper. 
     
     
       4. A multi-chip heat-sink cap combination according to  claim 1  wherein the chips are mounted on a substrate selected from the group consisting of alumina, aluminum nitride, glass ceramic, mullite, silicon carbide and beryllium oxide. 
     
     
       5. A multi-chip heat-sink cap combination according to  claim 1  wherein the thin film is deposited using chromium, nickel and gold as source materials. 
     
     
       6. A multi-chip heat-sink cap combination according to  claim 1  wherein the mating surfaces of the chips and the heat-sink columns are coated with the conductive thin film leaving a continuous margin (band) around the periphery of the chips and the heat-sink columns, the margin being 5 to 10% of half the width of the chips. 
     
     
       7. A multi-chip module and heat-sink cap combination manufactured by the process of: 
       providing a substrate With a plurality of chips fixed to and arrayed in a specific pattern thereon;  
       forming a heat-sink cap from a material having a coefficient of thermal expansion similar to that of the substrate comprising a plurality of individual heat-sink columns, each heat-sink column having a peripheral surface adapted to be bonded to a peripheral surface portion of a mating individual chip, the beat-sink columns interconnected by flexible members the heat-sink columns arrayed in an identical pattern to the chips on the substrate;  
       depositing a conductive thin film on that portion of the peripheral surfaces of the chips and the heat-sink columns that are to be bonded together with the conductive thin film having a continuous margin (band) around the periphery of the chips and the heat-sink columns, the margin being 5 to 10% of half the width of the chips;  
       assembling the substrate and the heat-sink cap with solder between mating portions of the heat-sink cap and the chips and between the heat-sink cap and the substrate; and  
       reflowing the solder to effect bonding of the heat sink cap to said substrate and said chips.  
     
     
       8. A multi-chip heat-sink cap combination according to  claim 7  wherein the heat-sink cap with the flexible connections between the heat-sink columns is formed as a unitary structure. 
     
     
       9. A multi-chip heat-sink cap combination according to  claim 7  wherein the heat-sink cap is formed from a material selected from the group consisting of aluminum nitride, aluminum-silicon carbide alloy, silicon carbide, copper-tungsten, aluminum, and copper. 
     
     
       10. A multi-chip heat-sink cap combination according to  claim 7  wherein the chips are mounted on a substrate selected from the group consisting of alumina, aluminum nitride, glass ceramic, mullite, silicon carbide, and beryllium oxide. 
     
     
       11. A multi-chip heat-sink cap combination according to  claim 7  wherein the thin film is deposited using chromium, nickel, and gold as source materials. 
     
     
       12. A multi-chip module and heat-sink cap comprising in combination: 
       a substrate with a plurality of chips fixed to and arrayed in a specific pattern thereon;  
       a heat-sink cap formed from a material having a coefficient of thermal expansion similar to that of the substrate comprising a plurality of individual heat-sink columns, each individual heat-sink column having a peripheral surface adapted to be bonded to a peripheral surface of a mating chip individual chip, the heat-sink columns interconnected by flexible members, the heat-sink columns arrayed in an identical pattern to the chips on the substrate;  
       a conductive thin film consisting of 0.1 μm chromium, 2 μm nickel and 0.5 μm gold deposited on the peripheral surfaces of the chips and the heat-sink columns that are to be bonded together with the conductive thin film having a continuous margin (band) around the periphery of the chips and the heat-sink columns, the margin being 5 to 10% of half the width of the chips; and  
       the substrate and the heat-sink cap soldered together between mating portions of the heat-sink cap and the chips and between the heat-sink cap and the substrate.  
     
     
       13. A multi-chip module and heat-sink cap according to  claim 12  wherein the heat-sink cap includes flexible connections between the heat-sink columns with the flexible connections formed as a unitary structure with the heat-sink columns. 
     
     
       14. A multi-chip module and heat-silk cap according to  claim 12  wherein the heat-sink cap is formed from a material selected from the group consisting of aluminum nitride, aluminum-silicon carbide alloy, silicon carbide, copper-tungsten, aluminum, and copper. 
     
     
       15. A multi-chip module and heat-sink cap according to  claim 12  wherein the chips are mounted on a subs rate selected from the group consisting of alumina, aluminum nitride, glass ceramic, mullite silicon carbide, and beryllium oxide.